This invention relates in general to certain new and useful improvements in safety interlock systems and, more particularly, to safety interlock systems which are especially designed to prevent theft or other unauthorized removal of automotive vehicles and like apparatus.
In recent years, theft of automotive vehicles has become quite prevalent and, in fact, has given rise to large-scale businesses based on stealing and resale of such automotive vehicles. In order to obviate this problem, various manufacturers of automotive vehicles and, in addition, various suppliers of safety systems and theft-prevention systems and the like have proposed alarm systems for use in these vehicles which advise of the potential theft or otherwise unauthorized removal of the vehicle. These alarm systems generally rely upon electronic sound alarms which are generated upon unauthorized attempts of removal. However, one skilled in these particular alarm systems is capable of short-circuiting the alarm system or otherwise removing the vehicle in such manner as to obviate the generation of the alarm signal.
There has been at least one proposal which utilizes an encoded switching system which must be actuated prior to operation of the vehicle. This encoded switch system essentially operates in the same manner as a combination switch which is designed to prevent operation of the vehicle until such time as the proper combination has been introduced into the switch to energize the same and in order to thereby operate the vehicle. While this interlock system certainly provides many advantages over the alarm system, these interlock systems are quite deficient in many respects. One of these deficiencies resides in the fact that these interlock systems can be easily obviated by one skilled in the art of unauthorizedly removing vehicles and the like. Furthermore, the conventionally available interlock systems are easily rendered ineffective by quickly determining the code through electrical signal measurements in the operation thereof.
In accordance with the safety switching systems of the type presently proposed, these systems rely upon a plurality of push buttons, or other switching inputs, which are actuated in order to produce a certain number of signals in proper sequence in order to open the interlock to thereby permit the starting of the vehicle. However, these systems utilize discrete components and, in addition, are designed so that one skilled in basic electronics can easily determine the encoding of the switching interlock. These systems utilize R-S flip-flops which operate silicon controlled rectifier circuits and which permit operation of the starter solenoid of a vehicle. In addition, these systems may also be connected to other components of the vehicle such as the fuel pump. However, these systems which use the discrete components are so designed in order to permit the energization of the vehicle, are also capable of having their coding easily detected, since the components of the circuit generally provide a 10-15-milliamp current. One skilled in the art of a basic electronic meter can easily detect the code by merely pressing the push button switches in order to determine the proper coding to operate the vehicle. Moreover, a relative inexpensive gauge can be used in a very short time by one basically informed in the use of this system so that the system has been quickly obviated.